To prevent generation of stress in assembly, so as to improve durability as a bearing, by fixing a layered flexure bearing group by a screw member through a pressing member capable of moving not turning in an axial direction on a fixed screw part tightening the layered flexure bearing group.

A layered flexure bearing group 17 is formed in a disk shape layered with a plate spring member 17. The plate spring member 17 is formed with three slits 171c extended in a volute shape to the periphery from the center in a part on a central ring between the center part in the periphery of a fixed center hole 171a and a peripheral edge part, in the peripheral edge part, a through hole 171b is formed. In a flexure bearing 17, when a nut 179 is fitted to a fixed screw part 16a3, a buffer material 180, fitting a key groove 180d of a shaft part 180b to a key 181 of a protruded part 16a2, is prevented from rotating in a peripheral direction. Consequently, the torque generated in the screw part is prevented from being transmitted to the individual flexure bearing.